Models for the Imaging of Ocean Gravity Waves by SAR-- Comparisons Of Theory And Experiment

Research over the past several years has produced a number of different mathematical models which all claim to explain the physical mechanism by which ocean waves are imaged by synthetic aperture radar (SAR). Identifying the correct and incorrect features in these models is important in two ways: first as basic research which leads to quantitative understanding of meteorological and oceanographic features in SAR images and second as a step in making, otherwise unobtainable, synoptic scale ocean wave measurements. Key issues connected with the differences between these models are the role of surface motion, degradation of SAR resolution by surface motion, relative importance of quasi-specular, Bragg-resonance and other scattering mechanisms and validity of two-scale models. Experimental results taken from SEASAT SAR images and buoy measurements of ocean waves are compared with hypotheses drawn from the three models. We conclude that for large scale, low amplitude surface waves, wave phase velocity is not a dominant factor in the SAR imaging process. Further, quasi-specular scattering can be important for SEASAT SAR imaging of ocean waves.